A multiple approach for evaluating the carotid and ocular circulations is being studied. The characteristics of ocular blood vessels are investigated by studying critical closure and vascular distensibility in the laboratory and clinical setting using perfusion techniques, carotid compression-tonography, and fluorescein angiography during induced ocular hypertension. The relationship between autoregulation of ocular blood flow, intraocular pressure, and venous pressure is being investigated. The ocular pulse was analyzed by graphic, Fourier, and differential techniques in animal experiments and in patients with angiographically demonstrated carotid occlusive disease. Carotid stenosis is associated with a decreased anacrotic slope, a reduced amplitude and area, and a loss of the dicrotic notch of the ocular pulse. Ocular pulse analysis appears to be more sensitive than ophthalmodynamometry in detecting carotid stenosis. A coefficient Pco, is being developed to reflect, in a quantitative manner, the altered carotid and ocular hemodynamics associated with carotid occlusive disease. This coefficient is determined by carotid compression-tonography using multiple plunger weights and appears to be elevated in the presence of carotid stenosis and decreased when there is inadequate collateral circulation to the eye being tested.